Blasting cap assembly



April 1953 L. s. CAGLE BLASTING CAP ASSEMBLY Filed Aug. 20, 1949 INVEN TOR Lg/ l burn S. Cagle ATTORNEY Patented Apr. 7, 1953 BLASTING CAP AS SEMBLY Lylburn S. Cagle, Bunker Hill, 111., assignor to Olin Industries, Inc., East Alton, 111., a corporation of Delaware Application August 20, 1949, Serial No. 111,435

This invention relates to electrically fired blasting caps and in particular to the provision of improved means whereby accidental firing of a cap through untimely contact of the lead wires with a source of electric current will be prevented.

In order to facilitate connection of electrically fired blasting caps with a source of electric current it is customary to have a short length of insulation removed from the ends of the wires leading from the caps. In order to avoid accidental ignition of such caps, it has also been common practice to provide a means for short circuiting the lead wires by connecting the bared ends of the wires until firing is to take place. Such means for short circuiting the lead wires is ordinarily referred to as a shunt. One means for shunting the lead wires which has been used in the trade for a number of years is that shown and described in the patent to Barab, U. S. 1,895,438 dated January 31, 1933. This comprises an eyelet of relatively soft metal having a peripheral groove in which the bared lead wires are clamped to provide the necessary short circuit. Insofar as short circuiting the lead wires is concerned, such a metal eyelet assembly has proven entirely satisfactory. However, occasional difiiculty is encountered in removing the metal eyelet from the lead wires when it is desired to fire the cap and on occasions the operators fingers have been scratched or cut, introducin considerable hazard into the operation. Furthermore, in clamping the bared lead wires about the eyelet body or in the removal of the eyelet therefrom, the wires occasionally are so bent or nicked that they break when an attempt is subsequently made to make connection with a source of electric current. This is not desirable since the operator must then take time to remove more insulation from the remaining lead wire or the blasting cap will not fire.

It is also common practice to identify each blasting cap as to size, type, etc. by means of an identification tag. Such identification tags have been fastened to the blasting cap or its lead wires in a number of ways, among which are to thread one of the lead wires through an eyelet hole near the end of the tag or by passing an auxiliary wire through the hole and then twisting the auxiliary wire about the lead wires. In all such instances the installation of the shunts and tags require two separate operations and likewise their removal requires two separate and sometimes difiicult operations when the blasting cap is put to use.

It is an object of this invention therefore to 1 Claim. (Cl. 102-28) provide means for short circuiting the lead wires and means for identifying the blasting caps which permit a more economical assembly and facilitate safe handling in the operations preceding firing. Another object of the invention is to reduce the number of operating steps necessary to attach the identification tag and short circuit the lead wires. Another object is to provide the lead wires of an electrically fired blasting cap with a shunt which is efiicient and yet may be removed from the lead wires by the operator without any hazard such as scratching or cutting his fingers. Still another object is to provide the lead wires of an electrically fired blasting cap with a shunt which upon assembly or removal does not tend to nick or otherwise weaken the bared ends of the lead wires. A still further object is to provide a shunt and identification tag both of which may be removed from the blasting cap lead wires in a single operation by merely pulling on the tag.

The foregoing objects and advantages as well as others which may become apparent from the detail description hereinafter, are accomplished in accordance with this invention by providing a blasting cap assembly in which a single eyelet both short circuits the wires leading from the blasting cap and attaches a tag thereto which may be used for identification. Inadvertent firing of the blasting cap is accordingly prevented and identification is accomplished by attaching the identification tag to the uninsulated free ends of the lead wires with an eyeletor grommet-shaped member, the rim of the eyelet hole of the tag and the uninsulated ends of the lead wires being disposed within the peripheral groove of the member. By thus combining the identification tag and the short circuiting member, two operations formerly necessary can be accomplished in one with a resulting reduction in manufacturing cost. Furthermore, the identification tag can be used as a handle or grip to readily remove the short circuiting member from the lead wires without mutilation of the operators fingers and without deleteriously bending or nicking the bared lead wires.

Having indicated in the foregoing in a general way the nature and substance of this invention, there follows a more detailed description of a preferred embodiment thereof with reference to the accompanying drawing in which:

Figure 1 is a perspective view illustrating a blasting cap assembly embodying this invention,

Figure 2 is an enlarged perspective view illustratmg the metallic shunt member, and Figure 3 is a perspective view of an identification tag, prior to assembly with the wires leading from the blasting cap,

Figure 4 is a back view of the tag, eyelet, and wire assembly illustrated in Figure 1, and

Figure 5 is an enlarged sectional view of the tag, eyelet and lead wire assembly taken at AA of Figure 1.

Referring first to Figure l, a casing l of any suitable material, as for example copper, such as is usual in blasting caps, contains the explosive.- The insulated lead wires 2 at one end are connected to a fusible filament Which is positioned in the .igniter material within the casing. l in the conventional manner. is customary is adapted to be fired electrically through the medium of the fusible filament connected across the lead wires 2. externally of the casing I are insulated except for a short length from their free ends as indicated at 4. The uninsulated free end portions of the lead wires permit connection to an electric circuit when the blasting cap is to be fired.

The shunt member, illustrated in Figure 2, may

be formed of any suitable material such as copi per, iron, etc., has a substantially circular or cylindrical body portion 5 aboutwhich the uninsulated lead wires are wrapped, and. a shoulder T which: prevents the lead Wires from slipping ofi one end-of the body portion 5. The body portion 5 is then inserted through the eyelet hole shown at 8 of the identification tag 3, Figure 3. If the tag 3 is formed of relatively thin or weak-material the rim of the eyelet hole 8 may be reinforced. to prevent the shunt 5 from tearing out of the tag. Such reinforcement may be accompliished by applying an additional layer of reinforcing. material on the eyelet end of the tag as illustrated in U. S. Patent 1,658,328, issued February 7, 1928, to Eastman, or in any other suitable manner. The end 6 of the shunt member, Figure 2, may be slitted or otherwise weakened for easy deformation and is then crimped as illustrated in Figure 4 to form a slotted shoulder holding the tag 3 and lead wires firmly between the shoulder I and. deformed end 8 but not so tightly as to prevent removal of the shunt by pulling thereon when it is. desired to fire the cap. As thus assembled the shunt member will preferably have the form of a ring having a peripheral groove with the tag and wires clamped therein and may be of any suitable or desired diameter. If desired the shunt member may besolid' rather than of ring. form or for example polygonal-shaped or the like, but a ring formis preferred from the standpoint of ease of assembly. Referring to Figure 5' it may be seen that the shunt is a rivetlike member holding the tag 3 and uninsulated lead wires 4 between'the shoulders 6 and 1 there- Of; either only partially or completely around the body 5 of the shunt and the shunt is preferably positioned near the end of the insulation onthe lead wires. Likewise the end portion 6- of the shunt maybe fashioned as a c'ontinuousshoulde'r, r;

as at l, or the shoulder I may be'fashioned-with slots asat end 6, so that both shoulders may be either continuous or slotted. Likewise, the identi- The igniter material as I Theuninsulated lead wires 4 may be vvrapp'ed portion 5 should be sufficiently long to accommo- The lead wires 2 date both the lead wires 4 and the tag 3.

As will be apparent from the foregoing specific embodiment, the identification tag is attached and the lead wires short circuited in a single clamping operation. When it is desired to use the blasting cap both the identification tag and shunt can be removed simultaneously in one operation, without deleterious deformation of the uninsulated ends of the lead wires or injuring the hands of the operator, merely by grasping. the identification tag firmly between the thumb and forefinger and pulling. It is contemplated this invention can be utilized even with blasting caps not requirin an identification tag, since the tag in such instances, whether printed, or otherwise marked, or plain, can still be used as a flap or tab for safely removing the shunt from the blasting cap lead wires. It is to be understood that the embodiment of the present invention as shown and described is only illustrative and that many changes may be made therein Without departing from the spirit and scope of the invention as set forth in the following claim.

Having thus described the invention what is claimed and desired to secure by Letters Patent In combination with a blasting cap adapted for electrical firing and provided with lead wires having uninsulated end portions, a tag having an eyelet hole, and a shunt member with a peripheral groove extending through said hole, said uninsulated end portions of the lead wires being wrapped around said shunt member and disposed in said groove so as to effect a contact between them per se, the ends of said shun-t member being flared to provide shoulders thereon with the rim of the hole in said tag and said wrapped end portions of the lead wires being held in position by compression between said shoulders, said tag having a portion extended from said shunt member as a handle for manually pulling said shunt member from said. wires.

LYLBURN S. CAGLE.

REFERENCES CITED The following" references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,895,438 Barab Jan. 31, 1933 i 1,897,685 Williams et al Feb. 14,1933

I FOREIGN PATENTS Number Country Date 238,640" Gr'eat Britain Aug. 27, 1.925 336,423 Great Britain Oct. 16', 1930 

